A bumper beam structure is known from Japanese Unexamined Patent Application Publication No. 2014-24394 that is formed of a laminate with a U-shaped cross section containing a continuous fiber reinforced resin layer and a discontinuous fiber reinforced resin layer and absorbs the collision energy by causing separation of the continuous fiber reinforced resin layer and the discontinuous fiber reinforced resin layer as well as separation of the fibers and resin in those fiber reinforced resin layers with input of collision load.
Another bumper beam structure is known from Japanese Registered Utility Model No. 2569826 that includes a honeycomb structure disposed in the center of the bumper beam in the vehicle width direction and resin foam members disposed at both ends of the bumper beam in the vehicle width direction such that the honeycomb structure and the resin foam members overlap each other at the boundary between them in the front-back direction, thereby preventing an abrupt change in the collision reaction force at the boundary between the honeycomb structure and the resin foam members both in a full flat collision and a pole collision so as to reduce damage to the bumper face.
Still another bumper beam structure is known from Japanese Patent No. 4295208 that includes injection molded resin members and resin foam members of a box shape alternately disposed on the bumper beam surface in the vehicle width direction and enables inexpensive production of bumpers of different models by varying the shape of the resin foam members.
In the bumper beam structure described in Japanese Unexamined Patent Application Publication No. 2014-24394, the center of the bumper beam whose lateral ends axe supported at the rear ends of the right and left rear side frames is curved like an arc toward the back. Thus, in order to minimize the deformation of the rear side frames when the bumper beam is hit from behind at a high speed, it is necessary to enhance the strength of the bumper beam to increase the amount of energy it absorbs. This can result in the rear side frames being deformed when the bumper beam is hit from behind at a low speed incurring an increased cost for repair.
The bumper beam structure described in Japanese Registered Utility Model No. 2569826 has a disadvantage of lower energy absorption because the collision energy is absorbed by the reaction force of the honeycomb structure and the resin foam member both when the bumper beam collides with a flat barrier and when it collides with a pole or a tree.
The bumper beam structure described in Japanese Patent No. 4295208 also has a disadvantage of lower energy absorption because, as with the bumper beam structure described in Japanese Registered Utility Model No. 2569826, the bumper beam absorbs the collision energy with the reaction force of the injection molded resin member and the resin foam member.
The present disclosure has been made in view of these circumstances, for example, and provides a vehicle bumper beam that protects the car body frame from deformation by effectively absorbing the collision energy both in a collision at a high speed and a collision at a low speed.